$10,000,000 sounds like the judgement I'd expect in a wrongful death suit, not a single episode of mud slinging. Not saying you're wrong I'm just surprised.
A man with a global audience accused another man, in multiple public statements, of pedophilia, sex trafficking, and statutorily raping his wife. When confronted with these statements, he doubled down each time and went further in his attack on the other man's character. Each of those, by itself, could constitute its own act of defamation per se. $10m being too much? On the contrary, $10m seems about right.
OTOH, if this was just one guy in a small town saying those same things about another guy, I'd be surprised if you even got into the six digits. Unfortunately for Elon, scope matters.
Sure, but that's enough money to retire comfortably at any age in a first world country. Did Musk do a lifetime's work worth of damage to the man? Did he make it impossible for the other man to work? Was the other man even fired? How many people actually believed Musk?
They other poster isn't pulling the numbers from somewhere to say Musk did a bad thing, they are analyzing his actual potential liability under existing law.
(so your questions are misdirected; they should be aimed at the people of California)
Take a look at comments on r/elonmusk or r/teslamotors, etc. Many people believe it, insisting that Mr. Musk probably hired a team of investigators to fact check and verify all his claims.
OTOH, if this was just one guy in a small town saying those same things about another guy, I'd be surprised if you even got into the six digits. Unfortunately for Elon, scope matters.